We already mentioned that the prototype of FGs is RX 11340.6+4018, presented in [1]}. A few years later, [2]} studied a sample of four X-Ray Overluminous Elliptical Galaxies: the authors claimed that these objects could have been part of the fossil category, but it was just a suggestion, since no operational definition was available until [3]} proposed the use of the magnitude gap as the discriminating factor between fossils and non-fossils, proposing a sample of 5 FGs in their work.
